S06 - Session P18 - Assessing the reliability of portable ion-selective electrodes proposed for the on-farm management of nutrient solutions and fertigation of horticultural crops

Authors: Gabriela Silva-Pumarada, Andy Blunk, Francesco Di Gioia *

Sustainable horticultural crop production systems designed for achieving high yield and quality standards, while minimizing the impact on the environment, require the adoption of rational nutrient management strategies. Monitoring tools are needed for real-time and site-specific management of crop fertilization. Portable ion-selective electrodes (ISEs) are proposed as potential tools for the rapid on-farm determination of specific ions in nutrient solutions, soil solutions, and plant sap. As new ISEs employing novel technologies become available, there is a need to assess their reliability as on-farm monitoring tools. A study was conducted to compare the features of two NO 3 -N ISEs to determine their susceptibility to the interferences of other ions. The interference of specific ions (Ca 2+ , K + , NH 4 + , Cl - , SO 4 2- PO 4 2- ) was assessed by measuring NO 3 -N concentrations in diluted solutions prepared using different salts such as KNO 3 , Ca(NO 3 ) 2 , NH 4 NO 3 , KCl, K 2 SO 4 , KH 2 PO 4 individually or in combination. Correlation and regression analysis was used to examine the relationship between calculated NO 3 -N and measured NO 3 -N concentrations, revealing the existence of a linear relationship between calculated and measured NO 3 -N. When measuring NO 3 -N concentrations within the recommended range by the ISEs manufacturer, limited interferences were observed in presence of other ions. While accuracy and feature differences were observed between the new ISEs tested, their susceptibility to the interference of other ions was substantially lower compared to the levels of interferences observed in previous generations of portable ISEs. Although ISEs cannot provide the same accuracy of laboratory analysis, the present study suggests that using adequate maintenance and calibration procedures and implementing adequate quality-assurance/quality-control measures to detect departure from linearity, the new ISEs tested are promising tools for the real-time on-farm monitoring of nutrient solutions. Additional research is warranted to evaluate the efficacy of ISEs in a field setting.